The subject matter described herein relates generally to powered rail vehicles.
Some known powered rail vehicles include one or more powered units and, in certain cases, one or more non-powered trailing units. The powered units supply tractive force to propel the powered units and trailing units. A “non-powered” unit generally encompasses any rail car without an on-board source of motive power. The non-powered trailing units hold passengers and/or goods. In some cases, the powered units may be referred to as locomotives and may include one or more traction motors. An alternator may be joined with an engine of the powered unit to generate electric current. The current is supplied to tractive motors that provide the motive force that propels the rail vehicle. The powered and/or trailing units may include additional, non-propulsion electric loads that do not propel the rail vehicle but provide other services for passengers. Examples of non-propulsion electric loads include heating, ventilation, and air cooling (HVAC) subsystems, lights, electric circuits for passenger use, and the like.
The non-propulsion electric loads may be powered by a Head End Power (HEP) system. Some known HEP systems provide power to non-propulsion loads that operate on a fixed voltage and fixed frequency electric current. For example, some known non-propulsion loads that draw power from HEP systems run off of three phase alternating current having a voltage of 480 volts and a frequency of 60 Hz. The HEP systems may receive electric current for the non-propulsion electric loads from the tractive circuit in a transformed manner. For example, a transformer may inductively couple the tractive circuit with an auxiliary circuit that supplies the current to the non-propulsion electric loads. In addition to or as an alternate to the transformer, one or more boost choppers may be provided to increase the voltage on the tractive circuit to a larger voltage on the auxiliary circuit. One or more filters between the tractive and auxiliary circuits may be necessary to remove unwanted frequencies of the current before supplying the current to the non-propulsion loads.
The boost choppers and/or transformers increase or decrease the voltage supplied to the auxiliary circuit from the tractive circuit. The engine of some known rail vehicles operates above a predetermined speed to ensure that sufficient voltage is supplied to both the tractive circuit and the auxiliary circuit. For example, during motoring of the rail vehicle, the engine may operate above a predetermined speed to ensure that sufficient voltage is generated and supplied to the tractive motors. When the rail vehicle is idling in a yard or building, the engine may still need to operate above a predetermined speed to ensure that sufficient voltage is generated and supplied to the non-propulsion loads of the auxiliary circuit. Such a running engine may create substantial and undesirable acoustic noise.
The transformers, boost choppers, and/or filters that are used to change the voltage or filter the current transferred between the tractive and auxiliary circuits may be relatively heavy and may substantially contribute to the weight of the rail vehicle. With increasing weight comes an increasing power demand of the tractive circuit and fuel consumption to propel the rail vehicles.
Some known rail vehicles include two or more separate engines that power the tractive and auxiliary circuits. One engine moves to cause an alternator to generate current for the tractive circuit while another engine moves to cause another alternator to create current for the auxiliary circuit. The inclusion of two or more engines to separately meet the power demands of the tractive and auxiliary circuits adds substantial cost and weight to the rail vehicle. For example, the use of two engines may increase the costs in maintaining the rail vehicle, and the weight of the rail vehicle is increased by the additional engine.
A need exists for a power distribution system of a rail vehicle that supplies electric current to meet the power demands of propulsion and non-propulsion electric loads while avoiding adding significant acoustic noise and/or weight to the rail vehicle, and/or cost in operating and maintaining the rail vehicle.